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![Old](/vbiis/images/statusicon/post_old.gif)
31-07-2017, 06:41 PM
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![vlazg's Avatar](../vbiis/customavatars/avatar17747_1.gif) |
Registered User
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Join Date: May 2014
Location: Darwin
Posts: 737
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Help with the Helix
I am planning on imaging the Helix nebula next and i would like some suggestions on what data to get.
20 minute subs Ha and O3, and maybe RGB for stars, is it worthwhile getting L as well or is it enough to use RGB to obtain L
For the narrowband, an equal amount of subs or more Ha than O3?
Thanks
George
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31-07-2017, 08:04 PM
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![RickS's Avatar](../vbiis/customavatars/avatar8703_1.gif) |
PI cult recruiter
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Join Date: Apr 2010
Location: Brisbane
Posts: 10,584
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Hi George,
No need for any Lum. The detail will come from the Ha and Oiii. The Oiii will be a lot dimmer than the Ha so you'll want to go heavier on the Oiii, at least if you want to try to bring out any of the interesting radial spiky structures.
Cheers,
Rick.
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![Old](/vbiis/images/statusicon/post_old.gif)
01-08-2017, 05:05 PM
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![vlazg's Avatar](../vbiis/customavatars/avatar17747_1.gif) |
Registered User
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Join Date: May 2014
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Quote:
Originally Posted by RickS
Hi George,
No need for any Lum. The detail will come from the Ha and Oiii. The Oiii will be a lot dimmer than the Ha so you'll want to go heavier on the Oiii, at least if you want to try to bring out any of the interesting radial spiky structures.
Cheers,
Rick.
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Thanks Rick, how would you combine the channels, Ha to red and the O3 to the G and B? What ratios would you use?
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![Old](/vbiis/images/statusicon/post_old.gif)
01-08-2017, 05:19 PM
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![RickS's Avatar](../vbiis/customavatars/avatar8703_1.gif) |
PI cult recruiter
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Join Date: Apr 2010
Location: Brisbane
Posts: 10,584
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Quote:
Originally Posted by vlazg
Thanks Rick, how would you combine the channels, Ha to red and the O3 to the G and B? What ratios would you use?
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Hi George,
IIRC, you're a PI user?
My usual approach these days is to match the intensities of the Ha and Oiii (using LinearFit) then make a straight HOO combine. Then I adjust the colour to taste using a combination of the Hue Curve in CurvesTransformation (brilliant for adjustments like pushing cyan to blue) and masks (mainly created with the ColorMask script) with a variety of other curves (R, G, B, a*, b*).
Some folks probably prefer to use various blends of Ha and Oiii as the R/G/B channel values to try to get closer to their desired colours with the initial combination. I used to do this but now I find I can usually push the colours where I want them to go, though it can take some effort!
The main reason I might go for an unequal HOO would be to get more Oiii to emphasise the spokes.
Here's an old Helix of mine that I'm pretty sure started as a straight HOO: http://www.astrobin.com/68705/?image...age=3&nc=&nce=
Hope that helps...
Cheers,
Rick.
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![Old](/vbiis/images/statusicon/post_old.gif)
01-08-2017, 05:33 PM
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![vlazg's Avatar](../vbiis/customavatars/avatar17747_1.gif) |
Registered User
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Join Date: May 2014
Location: Darwin
Posts: 737
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Quote:
Originally Posted by RickS
Hi George,
IIRC, you're a PI user?
My usual approach these days is to match the intensities of the Ha and Oiii (using LinearFit) then make a straight HOO combine. Then I adjust the colour to taste using a combination of the Hue Curve in CurvesTransformation (brilliant for adjustments like pushing cyan to blue) and masks (mainly created with the ColorMask script) with a variety of other curves (R, G, B, a*, b*).
Some folks probably prefer to use various blends of Ha and Oiii as the R/G/B channel values to try to get closer to their desired colours with the initial combination. I used to do this but now I find I can usually push the colours where I want them to go, though it can take some effort!
The main reason I might go for an unequal HOO would be to get more Oiii to emphasise the spokes.
Here's an old Helix of mine that I'm pretty sure started as a straight HOO: http://www.astrobin.com/68705/?image...age=3&nc=&nce=
Hope that helps...
Cheers,
Rick.
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Thanks Rick, helps a lot, i use PI so i will have a go when i get the data, i will have to wait for the colour mask script in the new release as i use a mac for processing.
If i can achieve any where near your image i will be over the moon
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![Old](/vbiis/images/statusicon/post_old.gif)
01-08-2017, 06:30 PM
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![RickS's Avatar](../vbiis/customavatars/avatar8703_1.gif) |
PI cult recruiter
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Join Date: Apr 2010
Location: Brisbane
Posts: 10,584
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You shouldn't have to wait very long for PI 1.8.5, George. Juan was talking about releasing it this week. I have been using an early version in anger for the last couple of weeks and it has been very solid.
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![Old](/vbiis/images/statusicon/post_old.gif)
01-08-2017, 08:38 PM
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![Somnium's Avatar](../vbiis/customavatars/avatar18465_1.gif) |
Aidan
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Join Date: Oct 2014
Location: Sydney
Posts: 1,669
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Hi George,
with my version of the Helix, i did 10 hrs of Ha and 8 hrs of Oiii http://www.aapodx2.com/2016/20161009.html
these were 20 min subs and it seemed to work though your set up will be completely different. i actually found that i would have liked more Ha data, there is no need for lum, but the more Ha data you can get the more you can bring out those fainter outer sections of the Helix that are spectacular. it depends on what the focus of your image is, if you want to capture the detail structure on the inner ring, go with more Oiii data, which is what i ultimately decided on. i didnt use any RGB data for the stars, if you want them to be anything other than white then you will need to do that
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![Old](/vbiis/images/statusicon/post_old.gif)
02-08-2017, 07:12 AM
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![vlazg's Avatar](../vbiis/customavatars/avatar17747_1.gif) |
Registered User
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Join Date: May 2014
Location: Darwin
Posts: 737
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Thanks Aidan,
i would like both in detail so i think i'll get as much Ha and O3 as boredom allows ![Big Grin](/vbiis/images/smilies/happy04.gif) and rgb later
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![Old](/vbiis/images/statusicon/post_old.gif)
02-08-2017, 09:48 AM
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![Camelopardalis's Avatar](../vbiis/customavatars/avatar15633_4.gif) |
Drifting from the pole
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Join Date: Feb 2013
Location: Brisbane
Posts: 5,429
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I'm not gunning for those awesome shots linked above, but after 2 hours I'm finally starting to see some of the outer nebulosity in Ha, and perhaps realise that my framing is about 90 degrees out
I'm attacking it with my Esprit 100 and ASI178 and 6nm Ha filter, 5 minute exposures seem to sky limit the subs, although I'm assuming this is because I'm in inner Brisbane.
Appreciate the OP bringing this up, as this seems to be quite a tricky target for being so popular
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02-08-2017, 10:19 PM
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![RobF's Avatar](../vbiis/customavatars/avatar5378_6.gif) |
Mostly harmless...
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Join Date: Jul 2008
Location: Brisbane, Australia
Posts: 5,716
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+1. I've been tuning my gear and automation on this one, but wasn't too sure where to start at processing time.
Thanks Rick and all for those pointers!
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